I clearly understand why dealers don't spend the money to detail and repair their used units. If they can't sell them, they have to wholesale them at auction. No dealer can afford to let a unit sit on their lot for a long time. Any money put into a unit is money generally not recovered upon the sale. That is why many dealers are willing to repair what the potential buyer requests upon completion of the sale but not before...and why many of the rigs they have are dirty and damaged.
What I took issue with in my OP is how can owners pay $75,000 plus for their new rig and then let it go to pot in a couple of years with no maintenance or repairs. They then want top dollar for their leaking, dirty, damaged rig because they still owe a lot on it. I have used every rig I have owned (now 3) to its fullest capabilities and yet managed to sell them quickly when that time came. The reason was because my rig stood out head and shoulders above what else was on the market.